The invention herein concerns a method of operation of a furnace for incinerating refuse, notably household refuse, commercial and industrial waste; this furnace comprised of a charging device for entering the waste into the upper part of a drying zone; this drying zone sits above a pyrolysis zone which in turn is above a combustion and melting zone, with a minimum of one orifice for removal of the volatile matter at the level of the drying zone and at least one orifice for the removal of the melted matter from the combustion and melting zone, with also one or more tuyeres to inject under pressure heated air with or without additional oxygen or pure oxygen into the combustion and melting zone.
A furnace of this type called simply "pyrolysis furnace" is described in German Offenlegungaschrift No. 2233498. Pyrolysis is a process of irreversable change produced by the action of heat in an environment deficient of oxygen. The pyrolysis zone of this type of furnace produces a distillation of the volatile fraction of the organic materials contained in the refuse fed into the furnace. The products of this pyrolysis are oxidized or melted in the lower combustion and melting zone and extracted as a liquid slag which is taken out of the furnace as a solid or granulate.
One particular problem of this type of furnace is the realization of a descending column of waste which occupies to a controlled height in the furnace the total volume therein and which can be renewed to the degree, by the feeding device above to which it is compacted, by drying and gasification in which it is consumed below. The method of attaining this condition is very difficult to realize and there forms very often a channel within the column of refuse, directly connecting combustion zone with the orifice for removal of the volatile products and short circuiting also the pyrolysis zone.
Experience has shown that it is very difficult to suppress a channel once it is formed. In effect even if the channel closes upon itself by the shifting of the refuse around it, or by the falling of refuse from higher levels in the channel, it will not disappear completely and the sort of plug formed in this way will not exist long prior to being consumed by the combustion products and oxygen emanating from the combustion.
As long as this channel exists, the majority of gases moving, ascend through it and the uniform distribution of the gases through all the volume of the furnace, indispensable to the proper operation of the process is far from guaranteed. It is given further that these channels generally form along the periphery of the furnace, the walls of which are exposed to higher temperatures than those intended for normal operation because of prolonged combustion in this channel, raising the risk of premature destruction of these walls by the elevated temperatures.